Composition and method for detection of demineralisation

ABSTRACT

The invention relates to a composition for the detection of tooth demineralisation. More specifically, the invention concerns a composition comprising a complex capable of producing an optical signal characteristic of the presence of free ions, the pharmaceutical uses of such a composition, and methods and a kit for the detection of active demineralisation at tooth surfaces using such a composition.

The invention relates to a composition for the detection of toothdemineralisation. More specifically, the invention concerns acomposition comprising a complex capable of producing an optical signalcharacteristic of the presence of free ions, the pharmaceutical uses ofsuch a composition, and methods and a kit for the detection of activedemineralisation at tooth surfaces using such a composition.

Tooth enamel contains large crystals of apatite, which form a tightlypacked structure; however tiny intercrystalline spaces or pores, whichare filled with water and organic material, separate the crystals. Theform of apatite found in teeth is hydroxyapatite, the smallest repeatingunit of which is Ca₁₀(PO₄)₆.2(OH). The components of the crystal can besubstituted. Known substituents include strontium, barium, lead, sodium,potassium and magnesium for calcium; the halogens (F, Cl, I, Br) forhydroxide and carbonate; and hydrogen phosphate for phosphate. Of thesesubstitutions fluoride and carbonate are reported to be the mostimportant, with fluoride preventing/repairing caries and carbonateincreasing susceptibility to caries. Many other ions such as zinc, tinand iron are also reportedly found in surface enamel. The organicmaterial (1% by weight, 2% by volume) found in fully formed enamelmainly consists of enamelins (mass 50-70 kDa), but also contains lowmolecular weight lipids, and some carbohydrate and organic acids such ascitrate and lactate. Enamelins can be detected by immunoblot analysis.

Many dental problems result from tooth demineralisation.Demineralisation is an underlying process involved in the development ofdental caries, tooth erosion and dentine hypersensitivity.Demineralisation of one or more of the dental hard tissues causes a lossof tooth integrity. Minerals are generally present in the dental hardtissues in a mineralised state and demineralisation involves the releaseof free ions.

Dental caries lesions damage the structure of teeth. The disease dentalcaries can lead to pain, infection, bad breath, foul tastes and toothloss. In severe cases, infection can spread to the surrounding softtissues, which can result in death. Factors inducing caries includebacteria, which collect around teeth in a sticky mass known as plaque,and ingested food and drink. The bacteria associated with earlydemineralisation are Streptococcus mutans, while lactobacilli appear tobe related to lesion progression. These bacteria convert sugars infood/drink into acids, such as lactic acid, through fermentation, and,if left in contact with teeth, these acids cause demineralisation. Thisremoval of mineral from the crystal surface of teeth makes the structuremore porous and susceptible to attack. As the pores increase in size,acid can penetrate deeper into the tissue and dissolve subsurfaceminerals. Demineralisation is eventually followed by disintegration ofthe organic material. If this is allowed to progress, mineral content islost to the extent that soft organic material left behind disintegratesforming a cavity or break in the surface integrity of the tooth. Thepresence of the plaque biofilm at the surface is essential if caries isto progress.

Technologies exist to determine the location and extent (depth and/orvolume mineral loss) of caries lesions. Identifying regions ofdemineralization is currently used by clinicians to detect caries andother dental problems. This may involve visual examination by aclinician, radiography or state of the art technologies such asDIAGNOdent (U.S. Pat. No. 4,290,433). Employing visual inspection todetect caries relies on the skill of the assessor and more importantlythe extent of demineralisation/erosion. Often significant damage willhave occurred by the time caries are detected this way. X-ray analysiscan reveal the presence of caries invisible to the eye however ongoingassessment is needed to determine caries activity. State of the arttechnologies that can aid in caries diagnosis include fibre opticillumination with light or lasers. DIAGNOdent (U.S. Pat. No. 4,290,433)and Quantitative Light-induced Fluorescence (QLF) (U.S. Pat. No.4,290,433) involve illuminating the tooth surface with red laser light(633 nm) or high intensity blue light respectively and then analysingthe emitted fluorescence. The nature of the emitted fluorescence can becorrelated with the degree of demineralisation in the tooth. Othermethods such as the ultrasonic caries detector (UCD) employ ultrasonicwaves (US2007238996) to create an image of the tooth, where the level ofreflectance is proportional to the density of the tissue; or Ramanspectroscopy (US2005283058) which is sensitive to mineral and crystalorientation to characterise the enamel surface.

Dental erosion is a progressive loss of hard tissue thicknessincrementally from the tooth surface and is frequently caused by acidicdrinks/foods (which may or may not be sugary), which causedemineralisation and can lead to exposure of the dentine. Erosion canalso be accelerated by tooth-brushing of acid-softened enamel (ordentine), leading to the complete removal of enamel and consequentexposure of dentine. Specifically, erosion refers to non-bacterialprocesses causing progressive loss of hard dental tissue. Tooth erosionoccurs when the enamel on your teeth is worn away by acid. Usually thecalcium contained in saliva will help remineralise (or strengthen) yourteeth after you consume small amounts of acid, but the presence of a lotof acid in your mouth does not allow for remineralisation. Acid can comefrom many sources, including carbonated drinks. All “fizzy” drinkscontain acid and can dissolve enamel very quickly. Increasing quantityconsumed leads to increased damage as does holding the drink in themouth for longer times. Pure fruit juice contains acid and thereforeacts in a similar way to carbonated drinks. Bulimia and acid reflux cancontribute to tooth erosion due to the exposure of teeth to stomachacids.

There are a number of signs of tooth erosion, ranging from its earlystages (sensitivity, discoloration, rounded teeth) to the later, moresevere stages (cracks, severe sensitivity, cupping). Wearing away ofprotective enamel leads to increased exposure of nerve endings in dentalpulp leading to pain when you consume hot, cold, or sweet foods anddrinks. The patient may therefore often present with sensitivity. Severesensitivity may develop as more enamel is worn away and teeth becomeincreasingly sensitive. Patients may also present with discolouredteeth, as they can become slightly yellow when the dentin is exposed.Teeth may have a rounded or “sand-blasted” look as a result of erosion.Front teeth may appear slightly transparent near the biting edges.Advanced discoloration may result—teeth may become more yellow as moredentin is exposed because of the loss of tooth enamel. Small cracks androughness may appear at the edges of teeth, and cupping may occur assmall dents may appear on the chewing surface of the teeth. Fillingsalso might appear to be rising up out of the tooth. If tooth erosion canbe identified early, then treatment can be applied and teeth protected.For example, problem areas may be sealed to prevent furtherdemineralisation. Early detection and diagnosis are therefore paramount.

Dentine hypersensitivity is the pain arising from exposed dentine,typically in response to external stimuli (and which cannot be explainedby any other form of dental disease). The exposed open dentinal tubuleslead directly to pulp tissues, which include the nerves within it. Whenthe cementum covering root dentine is no longer present (due to erosionor abrasion) after the gums have receded, tubules are exposed andsensitivity and pain can occur. In cases of hypersensitivity, thedentine has up to 8 times more tubules open at the dentine surface andthe tubule diameter is wider than when no pain is present. This providesa greater available surface area for demineralisation, such as by acidicdrinks and also leads to the release of more calcium followingapplication of such products.

As mentioned above, the development of caries, erosion orhypersensitivity is caused by a loss of tooth integrity throughdemineralisation of one or more of the dental hard tissues.Hydroxyapatite, the main component of enamel becomes soluble whenexposed to acidic environments. Teeth are under constant attack fromtheir external environment. Plaque bacteria on the tooth surface produceacids and after sugary meals or snacks, the acidity of the plaque canincrease dramatically. During exposure to any acidic environment,portions of inorganic material content at the surface of the teethdissolve and can remain dissolved for over 2 hours. Acid can permeatethe microscopic pores created by this surface demineralisation and asub-surface demineralised layer within the tooth can be created as thesurface layer partially remineralises as the plaque acidity returns tolower levels. Oscillating periods of demineralisation andremineralisation are therefore a “normal” feature at the surface ofteeth in the presence of plaque.

Dentine and cementum are more susceptible to acid demineralisation thanenamel, as they have a lower mineral content. The caries process is adynamic one which starts at the surface of a tooth, but due to complexdemineralisation-remineralisation processes related to mineralconcentration gradients in the fluid within the tooth and plaque, thesurface becomes more highly mineralised than the sub-surface region.Substitution readily occurs in the inorganic structure of enamel, and sodemineralisation also results in the release of many different ions.This factor is especially important for early detection, as the enamelsurface is the location of initial uptake and is also the very firstpoint of acid attack.

Common substituents include sodium, magnesium, fluoride and carbonate.Magnesium and carbonate can penetrate into enamel and are known tochange the crystal structure of apatite so that it becomes more soluble;therefore these ions are preferentially lost from the subsurface uponacid attack. Higher concentrations of zinc, lead, tin and iron are alsofound in surface enamel compared with deeper layers. Analysis of cariouslesions in enamel usually shows high levels of fluoride together withappreciable levels of magnesium, which is believed to be due to therapid uptake of these ions by the newly exposed layers of apatite.

Although some technologies exist to determine the location and extent(depth and/or volume mineral loss) of caries lesions, a major drawbackof these methods is that they do not address the nature of the cariesprocess i.e. if they are active or inactive at any one specific point intime. Inactive caries lesions may not require treatment, whereas activecaries lesions will (by definition) indicate ongoing demineralisation.It would also be beneficial to have information about demineralisationas early as possible. Often active caries will remain undetected untillate in the process and significant damage has been done to theintegrity of the tooth. Sometimes it is only when the patient starts tofeel pain that an X-ray is used to confirm the presence of caries.Currently, the active nature of the caries can only be determined byassessing progress of the caries lesion over time, typically during aperiod of more than a year in the case of radiographs (X-rays). Ifcaries, tooth erosion or hypersensitive teeth can be identified early,then treatment can be applied and teeth protected. For example, problemareas may be sealed to prevent further demineralisation. Early detectionand diagnosis are therefore paramount. Further, it is preferable thatinformation about activity is captured in one examination.

Initial caries diagnosis involves inspection of all visible toothsurfaces, often using a dental explorer, or metal pick, and mirror,illuminated by a bright light source. In some cases, the sign of acarious lesion or of demineralisation of enamel is the appearance of achalky white spot on the surface of a tooth. However such a spot is notalways visible.

A common technique to diagnose early caries is to blow air across thesuspect surface. The resulting loss of moisture from the surface changesthe optical properties of the demineralised enamel, allowingvisualisation of a white spot lesion indicative of early caries. As itcontinues to demineralise, caries may turn brown and eventually developinto a cavity. Large caries lesions are often visible to the naked eye.However, smaller lesions can be very difficult to identify. Once acavity forms, the lost tooth structure cannot be regenerated. Theprocess before this point is potentially reversible, therefore it isessential to identify caries as soon as possible.

State of the art technologies that can aid in caries diagnosis includefibre optic illumination with light or lasers. Diagnodent is atechnology covered by U.S. Pat. No. 6,769,911, whereby a tool containinga probe element and an integrated red light source induces fluorescencein the bacterially-infected carious region of a tooth, which afterpassing through an appropriate filter, is measured by the device.However, this method provides no indication as to whether the caries isactive or inactive.

Dyes, including fluorescent dyes, have also been used to identify thelocation of bacteria and presence of acid on teeth as a method to detecttooth decay. However, these dyes tend to be toxic and so areinappropriate for in-mouth analysis. Furthermore, enamel isauto-fluorescent and so background fluorescence can be prohibitivelyhigh.

Erosion is detected by visual inspection, as for caries detection. Signsand symptoms that indicate erosion include increased transparency ofincisors, fillings raised above the surrounding teeth, and wear onnon-biting surfaces. These all take time to develop to a visible degree,and the damage will already have been done. It would be desirable tohave a method for testing demineralisation as a result of erosion, for anumber of reasons. For example, certain foods or drinks could be appliedto teeth, followed by the disclosing composition. The disclosingcomposition would emit a detectable signal if ions were being emitted asa result of the food or drink being in contact with the tooth. Amanufacturer to determine how potentially damaging an edible productcould be to teeth could use this test, either to measure standard foodor drink products, or in the development of tooth-friendly products (lowpotential to cause erosion) or erosion prevention products such astoothpastes and sealants. A dental clinician may also use the disclosingcomposition to determine a patient's susceptibility to erosion and asdetermined by tooth composition and saliva.

Dentine hypersensitivity will be reported by the patient andinvestigated by a dentist. Useful diagnostic tools are the air/watersyringe, dental explorer, percussion testing, bite stress tests, andother thermal tests such as an ice cube and assessment of occlusion.However, these methods, based on the patient's report, are subjectiveand lack accuracy.

It is an object of the invention to mitigate problems such as thosedescribed above.

According to a first aspect of the invention, there is provided apharmaceutical composition comprising a complex capable of producing anoptical signal characteristic of the presence of free ions.

According to a second aspect of the invention there is provided acomposition for use in detecting active dental caries and/or activetooth demineralisation due to erosion, comprising a complex capable ofproducing an optical signal characteristic of the presence of free ions.

The complex for detection may be a dye, synthetic ion chelator such asan EDTA-reporter complex or a macrocycle such as a crown ether reportercomplex, a protein or protein-reporter complex, a molecular imprintedpolymer-reporter complex or molecular probe such as holliday junction.One or a combination of these complexes may be used, for example ifdifferent ions are to be detected.

The ions to be detected may comprise calcium ions, magnesium ionsphosphate ions, carbonate ions, potassium ions, strontium ions, fluorideions copper ions, chloride ions, zinc ions, lead ions, tin ions, ironions or organic material such as enamelins. Detection of different ionsmay help to determine the location of demineralisation and its depthinto the dental hard tissues, because, as described herein, differentions may be present in different dental hard tissues.

The composition may further comprise a pharmaceutically acceptableadditive and the additive is preferably a bactericidal or bacteriostaticagent.

The composition may comprise a pharmaceutically acceptable excipient andthe excipient is preferably a flavouring or colouring additive.

It is preferred that the composition is in a pharmaceutically acceptabledosage form and the composition is preferably a liquid, a powder or agel. The composition may comprise from 1 ng/ml to 10 mg/ml complex, orany concentration that gives a significantly high signal to noise ratio.

The composition may comprise a protein or a protein complex. Such acomplex may undergo a conformational change on binding free ions thatleads to an optical signal being generated.

It is preferred that the protein or protein complex comprises aequorin,obelin, clytin, mitrocomin, halistaurin, phialidin, mnemiopsin,symplectin, gr-bolinopsin, casein, calsequestrin, calexcitin, calciumbinding cysteine protease, calmodulin and other EF hand proteinsorberovin. The person skilled in the art would be aware of other proteinsor protein complexes that are functionally similar and which could beselected without undue effort.

It is preferred that the protein or protein complex comprises tandemfusions of fluorescent proteins and ion binding proteins such ascalmodulin, a calmodulin-binding peptide (M13), and an enhanced green-or yellow-emitting fluorescent protein.

As an alternative, the complex may fluoresce at a characteristicwavelength indicative of the presence of ions.

The composition may comprise both a protein or protein complex whichproduces an optical signal on binding with free ions, and a protein orprotein complex which fluoresces at a characteristic wavelengthindicative of the presence of ions.

These may be modified, for example by altering the DNA sequence of thegene, by acetylation, ethoxycarbonylation, fluorescamine-modification orfluorescein labelling or by creation of chimeric proteins such as aGFP-aequorin (US2003175807) to enhance the signal, prolong the durationof signal or alter its emission spectra. Proteins and protein complexeswith similar function, such as those undergoing a conformation change onbinding an ion that leads to an optical signal may also be used.

The protein or protein complex preferably comprises a recombinantprotein (expressed to a high purity). The protein or protein-proteincomplex may be administered in a solution free of the specific ion inorder to reduce background signal. This may be achieved using an ionchelator.

Preferably, the composition will be optically transparent. This willallow the composition to transmit light emitted on contact of theion-sensitive reporter with the free ions. Additives may also be addedto alter the signal for example, a gel to extend the length of time thatthe detectable signal remains detectable, buffers to optimise thereaction or modified substrate to prevent immediate flash, but which canbe triggered later such as the Enduren system for coelenterateluciferases.

The optical signal produced by the composition on exposure to free ionsmay be detected by a spectrophotometer, charge coupled device (CCD),complementary metal-oxide semiconductor CMOS, digital camera,intensified camera, intraoral camera, videoscope, photographic film,fibre-optic device, photometric detector, photomultiplier,micro-electro-mechanical system (MEMS) or visually by eye.

According to a third aspect of the invention, there is provided the useof a pharmaceutical composition as described above for the manufactureof a preparation for the detection of dental caries. Active dentalcaries can be differentiated from inactive dental caries, on the basisof the presence of demineralisation, the composition may therefore beused in the manufacture of a preparation for use in the differentiationbetween active and inactive dental caries.

According to a fourth aspect of the invention, there is provided the useof a pharmaceutical composition as described above for the manufactureof a preparation for the detection of active tooth demineralisation dueto erosion.

According to a fifth aspect of the invention, there is provided the useof a pharmaceutical composition as described above for the manufactureof a preparation for the detection of sites of dentine demineralisationrelated to dentine hypersensitivity.

According to a sixth aspect of the invention, there is provided a methodfor the detection of active tooth demineralisation, comprising the stepsof exposing a tooth to a composition as described hereinabove; anddetecting the resulting optical signal.

The method may include the additional step of marking regions of thetooth or tooth model in order to allow identification of particularregions of the tooth or tooth model. It can be difficult to ensure thatthe same area of a tooth or tooth model can be monitored and may aidfuture analysis such as when comparing data from different techniques orfor monitoring progression of a disease or treatment over time. Such amark may be made with dye, pencil or by attaching a grid, such as thatmade out of copper wire to the tooth, such as with nail varnish.

The method may further comprise the step of exposing the tooth to asensitising solution prior to exposure with the composition. Thesensitising solution may be an acidic or a sugary (where plaque ispresent) solution. This may allow the susceptibility of the tooth toerosion to be determined. This could be used in order to assess anindividual's susceptibility to tooth erosion. This method could also beused to assess the dental erosive properties of food or drink products.

The method may further comprise the step of allowing a period of time tolapse in between applying the sensitising solution and applying thedetection composition. This is to allow the saliva in the mouth to buildup, and allows the user to assess the protective effect of the saliva.This period of time may be, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10,11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28,29, or 30 seconds but may be any other time deemed necessary in order toallow the saliva to return to its normal volume and composition in themouth, for example, a minute, two minutes or up to five minutes may berequired. The length of time required will depend on the volume and theflow of saliva in the individual patient and can easily be determined bythe person skilled in the art.

The optical signal may be detected by means of a spectrophotometer,charge coupled device (CCD), complementary metal-oxide semiconductorCMOS, digital camera, intensified camera, intraoral camera, videoscope,photographic film, fibre-optic device, photometric detector,photomultiplier, avalanche photodiode, light sensitive array,micro-electro-mechanical system (MEMS) or visually by eye.

According to a seventh embodiment of the invention, there is provided akit for use in detecting demineralisation, comprising a compositioncomprising an ion-sensitive complex, means for applying the compositionand a detector unit. The kit may also include an acidic or sugarysensitising solution. The kit may further include a marker such as agrid for marking areas of interest on a tooth or tooth model. The kitcould be purchased, for a number of reasons. A dentist may wish to havea convenient commercially available test kit for use in assessing apatient's susceptibility to erosion. A home-use test of erosionsusceptibility could be used by a consumer, who could then decide whatpreventative measures to take. Manufacturers of food or drink productscould purchase the test if the tooth-eroding properties of theirproducts are of interest.

Thus, the invention seeks to provide a composition and a method usingsuch a composition for the detection of free ions in dentalapplications.

The invention will be further described by way of example only and withreference to the accompanying figures in which:

FIG. 1 is a schematic representation of FRET in cameleon indicators;

FIG. 2 shows extracted premolar teeth with masked ‘windows’ marked onthe surface thereon;

FIG. 3 shows images of extracted teeth following application of acid geland disclosing gel;

FIGS. 4 and 5 demonstrate the use of an image analysis programme ImageJto determine the brightness of the area treated with acid gel anddisclosing gel;

FIG. 6 demonstrates the use of obelin as a disclosing composition;

FIGS. 7 a to 7 b show the results of experiments carried out on the rootof a tooth with a caries;

FIGS. 8 a and 8 b show the results of experiments carried out on thedentine on a tooth;

FIGS. 9 a to 9 b show the results of experiments carried out in relationto cavity identification;

FIGS. 10 a to 10 b show the results of further experiments carried outin relation to cavity identification;

FIGS. 11 a to 11 b show the results of further experiments carried outin relation to caries identification;

FIG. 12 shows images of deciduous molars with cavitated lesions (A).FIGS. 12 a and c show images of the teeth in the light and FIGS. 12 band 12 d show monochromatic image following application of disclosinggel;

FIG. 13A shows an incisor (deciduous) with a large caries lesion (knownas nursing bottle syndrome), the image of the tooth taken in the light;

FIG. 13B monochromatic image of an incisor (deciduous) with a largecaries lesion (known as nursing bottle syndrome) following applicationof disclosing gel;

FIG. 14A is an image showing the smooth surface of a molar (deciduous),the image of the tooth in the light;

FIG. 14B is a monochromatic image showing the smooth surface of a molar(deciduous) following application of disclosing gel;

FIGS. 15A and 15B shows images of the occlusal surface of molar(permanent). FIG. 15A shows an image of the tooth in the light FIG. 15Bshows a monochromatic image following application of disclosing gel;

FIG. 16A is an image of a molar (deciduous) taken in the light;

FIG. 16B shows a monochromatic image following application of disclosinggel;

FIG. 16C is a graphical representation of the light generated across alesion;

FIG. 17A shows an x-ray of permanent molars;

FIG. 17B shows permanent molars whose mesial surface was alsoinvestigated with x-ray then disclosing gel;

FIG. 18A shows an image of a tooth that had been rinsed in deionisedwater and removed before being assessed;

FIG. 18B shows a tooth that had been rinsed and assessed in saliva;

FIG. 18C shows a tooth that had been rinsed in saliva but removed beforebeing assessed;

FIG. 18D shows a tooth that had been incubated in saliva, removed, andrinsed in deionised water before being assessed;

FIG. 19A shows supra-gingival calculus imaged following addition ofdisclosing solution;

FIG. 19B shows sub-gingival calculus and imaged following addition ofdisclosing solution;

FIG. 20A shows an image of the tooth in the light following applicationof disclosing gel; box indicates area of calculus;

FIG. 20B shows a monochromatic image following application of disclosinggel; box indicates area of calculus;

FIG. 21A shows images of the occlusal surface of molar (permanent) inthe light prior to application of disclosing gel;

FIG. 21B monochromatic image of the occlusal surface of molar(permanent) following application of disclosing gel;

FIGS. 22 a to 22 c show the results of experiments carried out inrelation to dental erosion and hypersensitivity;

FIGS. 23 a to 23 c show the results of further experiments carried outin relation to dental erosion and hypersensitivity;

FIGS. 24 a to 24 c show the results of yet further experiments carriedout in relation to dental erosion and hypersensitivity;

FIGS. 25 a to 25 c show the results of experiments carried out usingacid etched teeth;

FIGS. 26 a to 26 d show the results of further experiments carried outusing acid etched teeth;

FIGS. 27A and 27B are graphs showing the protective effect of saliva onthe acid-treated enamel compared to deionised water;

FIG. 28 is a graph showing the effects of solutions of differing pH ondifferent levels of demineralization, as measured by a change inbrightness, with solutions of lower pH generating more demineralization(more brightness); and

FIG. 29 is a graph indicating that the effect of foodstuffs ondemineralization of teeth can be determined using the disclosingcomposition and assay method of the invention.

In the context of the invention, an “ion-sensitive complex” means acomplex capable of producing an optical signal characteristic of thepresence of free ions released as a result of demineralisation. Thecomplex may be a dye, synthetic ion chelator such as an EDTA-reportercomplex or a macrocycle such as a crown ether reporter complex, aprotein or protein-reporter complex, a molecular imprintedpolymer-reporter complex or holliday junction. which may be modified toincrease sensitivity to ions, to improve signal strength, to prolongsignal, to improve signal to noise, to improve spectral response.Recombinant or modified protein may also be used.

The invention concerns the novel pharmaceutical use of one or acombination of ion-sensitive dyes, synthetic ion chelators such as anEDTA-reporter complexes or macrocycles such as a crown ether reportercomplexes, protein or protein-reporter complexes, molecular imprintedpolymer-reporter complexes or molecular probes such as hollidayjunctions as reporters in the detection of dental demineralisation. Asdiscussed above, the presence of free ions at the tooth surfaceindicates the presence of demineralisation. These reporters can be usedto detect the presence of free ions on teeth, thus helping to detectspecific dental problems.

In the presence of free ions, an optical signal is emitted from theion-sensitive reporter. The spectra, intensity or duration of the signalis proportional to the quantity of free ions. Different tissues havedifferent amounts and types of ions available and so the response to theion-sensitive reporters will vary between tissues. In the process ofdental erosion dentine may eventually be exposed. In the process ofdentine hypersensitivity, cementum is removed and root dentine isexposed. Dentine and cementum are less mineralised than enamel and thusrespond directly to the ion-sensitive reporters. These demineralisedfeatures of teeth may be identified by areas having more intense opticalsignals.

In the presence of active caries, free ions will continue to be releasedas the tooth is demineralised by the acidic environment and bacteria.The localisation and intensity of this signal allow the localisation ofthe active caries to be determined.

The composition may contain one or more of the following: dye, syntheticion chelator such as an EDTA-reporter complex or a macrocycle such as acrown ether reporter complex, a protein or protein-reporter complex, amolecular imprinted polymer-reporter complex or molecular probe such asholliday junction. The protein or protein complex may include ionsensitive photoproteins, ion sensitive fluorescent proteins, or proteincomplexes detectable by fluorescence, bioluminescence, chemiluminescenceor fluorescence resonance energy transfer (BRET, CRET or FRET)),labelled antibodies which recognize organic material e.g. enamelins Thesynthetic ion chelator or protein complexes may incorporate afluorescence moiety which is quenched on ion binding, or proteincomplexes which incorporate a fluorescence moiety and quencher, thelatter which is removed on binding of the ion causing a release oflight.

Different ions may be detected using different complexes. Magnesium isdetected with fluorescent dyes such as Mag-Fura-2 and Mag-Fura-5. Theycould be used to measure magnesium in situ (excitation 340-380 nm,emission 500-510 nm). Preferably the dyes are not toxic.

A number of dyes are calcium sensitive but may be too toxic to use inmouth. Fura-2, Calcium Green-1, Fluo-3, Indo-1 and cSNARF-1 are allfluorescent dyes, which bind to free intracellular calcium. Indo-1 andcSNARF-1 are dual emission dyes. Fluorescent calcium binding dyes usedto detect and measure free calcium may be useful as an alternative toluminescent photoproteins. Furthermore, these dyes may be used in anovel method for simultaneous measurement of Calcium and Strontium insaliva if used in conjunction with Halistaurin. Fura-2, Calcium Green-1,Indo-1 and their actetomethyl ester derivatives have been used in mice(in vivo) to monitor neuronal activity. Rhod-2 is also a calciumsensitive dye although it is less sensitive than Fluo-3. The longerexcitations and emissions wavelengths of Rhod-2 (˜556/576 nm) make theindicator useful for experiments in cells and tissues that have highlevels of autofluorescence and for experiments where another fluorescentdye of shorter wavelengths is used at the same time. As enamel is knownto fluoresce, such long emission wavelength would be a significantadvantage.

Detection of fluoride may be achieved with fluorescent dyes. High levelsof fluoride are generally found in caries lesions, believed to be due tohigh uptake of the ion at sites of demineralisation. There has been andcontinues to be a great deal of research into fluoride sensitivefluorescent systems for both industrial and medical applications. Onesuch complex is Zr(IV)-EDTA-oxine which exhibits a decrease influorescence upon fluoride binding. Fluoride sensors displaying anincrease in fluorescence in the presence of fluoride have also beenreported; these include boronic acid compounds and thioureidonaphthalene derivatives. The boronic acid compounds are currentlyrelatively insensitive (detection level 50-70 mM), however it isbelieved that with the appropriate modifications fluoride selectivitycould be fine tuned to any desired concentration range. The novelthioureido naphthalene derivatives exhibit a 40-fold increase influorescence in presence of fluoride, and have a very high selectivityfor fluoride over other halogens. Alternatively, (Tae-Hyun Kim andTimothy M. Swager (2003, Chem. Int. Ed. Angewandte 42, 4803-4806)describes a system whereby the cleavage of a Si—O bond by fluoride leadsto the formation of a highly fluorescent coumarin molecule.

Detection of potassium may be with a fluorescent dye such as SBFI, whichis both potassium and sodium sensitive (excitation 340-380 nm, emission510 nm). Potassium is linked to dental hypersensitivity and possiblycaries. Alternatively, a photoprotein, derived from okinawan squid(Symplectoteuthis oualaniensis) is sensitive to potassium and may beused (US2004191884).

Where the composition includes a protein or protein complex, it mayproduce an optical signal on binding with free ions. Such a protein orprotein complex may be modified, for example by altering the DNAsequence of the gene, by acetylation, ethoxycarbonylation,fluorescamine-modification or fluorescein labelling or by creation ofchimeric proteins such as a GFP-aequorin (US2003175807) to enhance thesignal, prolong the duration of signal or alter its emission spectra.Proteins and protein complexes with similar function, such as thoseundergoing a conformation change on binding to ion or organic materialthat leads to an optical signal may also be used.

Examples of such protein or protein complexes are photoproteins.Photoproteins are stable enzyme-substrate complexes consisting ofpolypeptide chain(s) and an oxygen-preactivated substrate, such as2-hydroperoxycoelenterazine, which is tightly but noncovalently boundwith the protein. Bioluminescence may be triggered by, for example, Ca²⁺and results from decarboxylation of the substrate bound with theprotein. Another photoprotein which may be of use according to theinvention is halistaurin. Halistaurin can be used to detect strontium,which is thought to replace a small fraction of the calcium in thehydroxyapatite crystal during mineralization. Deficiency in strontium islinked to dental caries (“Strontium and dental caries”. Nutr Rev 1983;41:342-344). Detection of strontium may be with a photoprotein such ashalistaurin. Wide ranges of values of strontium in teeth (e.g. 66-564ppm) have been reported from different areas in US

Another example of a photoprotein is aequorin, which naturally occurs inthe bioluminescent jellyfish, Aequorea victoria or can be expressedrecombinantly. Aequorin is a protein capable of storing a large amountof energy, which is released in the presence of calcium. Apoaequorininteracts with its substrate coelenterazine to form a relatively stablecomplex, which is activated by calcium. The binding of two calcium ionsto aequorin causes conformational changes of the protein, resulting inthe opening of the protein and decomposition of coelenterazine peroxideto coelenteramide and CO₂, accompanied by emission of an optical signalor light. Further description of aequorin may be found in Shimomura etal (1978) Proc. Natl Acad. Sci. U.S.A. 75, 2611-2615; Head et al (2000)Nature 405, 372-376; and Shimomura (2005) Journal of Microscopy 217,3-15.

Other examples of photoproteins include obelin, clytin, mitrocomin,halistaurin, phialidin, mnemiopsin, symplectin, gr-bolinopsin andberovin. These photoproteins show high sequence homology and containthree “EF-hand” calcium-binding sites. Further description of thesephotoproteins may be found in Prasher et al, Biochem. Biophys. Res.Commun. 126 (1985); Inouye et al, Proc. Natl. Acad. Sci. USA 82 (1985),pp. 3154-3158; Prasher et al, Biochemistry 26 (1987), pp. 1326-1332;Inouye et al, FEBS Lett. 315 (1993), pp. 343-346; T. F. Fagan et al,FEBS Lett. 333 (1993), pp. 301-305; Illarionov et al, Dokl. Akad. Nauk326 (1992), pp. 911-913; Illarionov et al, Gene 153 (1995), pp. 273-274;Shimomura et al (1985), Biochem J. Jun. 15; 228(3):745-9; Ward et al(1974) Biochemistry. Mar. 26; 13(7):1500-10. Further description of themode of action of these proteins may be found in Markova et al,Biochemistry 41 (2002), pp. 2227-2236; Charbonneau et al, Biochemistry24 (1985), pp. 6762-6771; Tsuji et al, Photochem. Photobiol. 62 (1995),pp. 657-661.

The composition may comprise a synthetic ion chelator such as anEDTA-reporter complex or a macrocycle such as a crown ether reportercomplex. There are many examples of these, which bind to ions andcomplexes with reporters have been made. For example, joining of afluorophore and selective receptors using photoinduced electron transferfor calcium using BAPTA as described in John F. Callan, A. Prasanna deSilvaa and Nathan D. McClenaghanv (2004) Chem. Commun. 2048-2049. AlsoU.S. Pat. No. 5,409,835 describes fluorescent calcium-bindingheterocyclic probe compounds for determining calcium ion concentrationin samples.

The composition may comprise a complex that fluoresces at acharacteristic wavelength indicative of the presence of ions. Suchfluorescent complexes respond to ions by altering the intensity orcolour of light. These complexes may be proteins or protein complexes.

Preferred examples of fluorescent proteins include, cameleon proteins orindicators. Cameleons are a new class of indicators for calcium ionconcentrations in living cells, which operate through a conformationalchange that results in “Förster Resonance Energy Transfer” (FRET or“Fluorescence Resonance Energy Transfer”) in the presence of calciumions. FIG. 1 shows a schematic representation of FRET in chameleonindicators. More specifically, FRET involves the non-radiative transferof excitation energy from and excited donor fluorophore to an acceptorfluorophore in the ground state by means of intermolecular long range(10-100 Å) dipole-dipole interactions. Cameleon indicators consist of anartificial protein modified from green fluorescent protein (GFP). Thecameleon molecular structure is modeled as a fusion product between twofluorescent proteins (having differing excitation and emissioncharacteristics), calmodulin (CaM), and the calmodulin-binding domain ofmyosin light chain kinase (M13). Calmodulin is capable of binding withfree calcium ions and the M13 chain can bind with calmodulin after ithas bound the calcium ions. The genes of these four proteins are joinedlinearly, and the fusion genes are expressed in a variety of cells. Whencalmodulin binds free calcium, it changes in structure, bringing the twofluorescent proteins closer together and results in FRET. Thus, insteadof the cyan fluorescent protein emitting blue light, this light istransferred to the yellow fluorescent protein, resulting in yellowfluorescence. Further description of cameleon indicators may be found inMiyawaki et al (1997) Nature 388 (6645):882; Miyawaki et al, Proceedingsof the National Academy of Sciences (USA) 96: 2135-2140 (1999).

A further example of fluorescent protein is Pericam, which is a modifiedform of GFP. The Ca²⁺-induced interaction between CaM and the bindingpeptide M13 of pericam leads to changes in the fluorescencecharacteristics of circularly permuted (cp)YFP as described in Nagai etal, PNAS 98 (6): 3197 (2001).

A further example of a fluorescent approach is the Camgaroo probe inwhich the binding of calcium interacts with calmodulin causing a proteinconformational change and an increase in fluorescence from the yellowfluorescent protein and induces an increase in fluorescence (as reviewedin Rüdiger Rudolf, Marco Mongillo, Rosario Rizzuto & Tullio PozzanNature Reviews Molecular Cell Biology 4, 579-586)

A further example of a fluorescent approach are the chimericfluorescent-photoproteins for example GFP-aequorin (such asUS2003175807) wherein the fluorescent molecule is covalently linked witha photoprotein and there is a transfer of the energy byChemiluminescence Resonance Energy Transfer (CRET).

These examples serve to illustrate the use of protein-reporter complexesin ion detection. The proteins involved may be any number that bind, orchange conformation on binding a particular ion. For calcium these couldbe casein, calsequestrin, calexcitin, calcium binding cysteine protease,calmodulin and other EF hand proteins. The reporters may be dyes orfluorescent or luminescent proteins.

The composition may comprise a complex incorporating a molecular probesuch as Scorpion probe, Taqman probe, holliday junction or linear probe.Fluorescence or luminescence may occur on ion binding to the probe.Preferred examples of molecular probes are Holliday junctions. These aremobile junctions formed between four strands of DNA. They are usuallyused for detection of specific DNA sequences, however, metal ions areknown to play an important role in determining the conformation of thejunction by binding to particular sites (Thorpe J. H., Gale B. C.,Teixeria S. C. and Cardin C. J. (2003) J Mol Biol. 2003 Mar. 14;327(1):97-109). These junctions could therefore be used to detect thepresence of ions such as sodium, calcium and strontium.

A number of methods may be used together. For example, chelators may beused to sequester one ion, leaving another to bind to a photoprotein.Thus the photoprotein halistaurin binds both calcium and strontium.Strontium may be a good measure of disease and the calcium, which wouldotherwise mask the amount of strontium present, could be sequesteredbefore the photoprotein is added to the tooth, leaving the photoproteinto respond only to the strontium. Calcium sequestering agents could beprotein based (calmodulin, calcyclin) or chemical based (BAPTA, EGTA).BAPTA (1,2-bis(o-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid) is acalcium-specific chelator, and BAPTA based compounds are among the mostpopular for measuring free intracellular Ca²⁺.

Photoproteins and fluorescent proteins may be used together usingBioluminescence Resonance Energy Transfer (BRET) in which the opticalsignal produced from a photoprotein is transferred to a fluorescentprotein in close proximity, and fluorescence from the fluorescentprotein is then measured. In this manner, the colour of the signal maybe altered or the duration of the signal increased to improve imaging.One of the problems with imaging fluorescent dyes on teeth is that thereare often situations where it is not practical to use a high intensitylight source due to the intrinsic high auto-fluorescence of teeth. Onepossible benefit of using BRET is that it can be used for the excitationof a fluorescent probe that is co-localised in a specific area wherecalcium is present

The composition may be used for in-mouth analyses, for example to detectthe presence of active caries; and out-of-mouth analyses, such as in alaboratory for the study of artificially induced caries, development ofnew tooth-friendly foods and formulations and study of the erosivity offoodstuffs. Out of mouth analyses using the composition may also becarried out using a tooth model, such as hydroxyapatite models or enamelsections.

The composition may be used for example by dentists and dentalhygienists, for early detection of active demineralisation,determination of the best treatment, for monitoring a problem ortreatment over time, and identifying individuals who may be susceptibleto certain dental problems (e.g. erosion or hypersensitivity); bylaboratory researchers for the development of novel products (e.g.toothpastes, drinks); or for the home care market for detection andassessment of active dental disease (e.g. in the form of a mouthwash ordisclosing tablets).

No single-step method for the detection of active caries is currentlyavailable. Active caries tend to produce free ions due to continueddemineralisation; inactive caries will produce few, if any, free ions,due to the absence of demineralisation. Demineralisation may be detectedby measuring the optical signal output following application ofion-sensitive reporters, this may be compared to non-active caries wherethere is little or no demineralisation.

Ion-sensitive reporters can therefore provide a one-time measure of theactive nature of caries, and eliminate the need for multiple visits tothe dentist. Ion-sensitive reporters may also be used to determine thesusceptibility of an individual to dental disease, for example, dentalerosion. In this case, a mildly eroding solution e.g. weak acid could beadded to teeth and the response of the teeth as measured by a signalemitted by the detection composition would indicate the extent ofdemineralisation and likelihood of encountering problems with erosion inthe future.

The method for the detection of active tooth demineralisation mayoptionally include the steps of removing saliva from the tooth surface,and where appropriate removing plaque (if present), then exposing thetooth surface under investigation to a composition as described aboveand detecting the resulting optical signal.

The method may further comprise the step of exposing the tooth to asensitising solution, such as a sugary or acidic solution, prior toexposure with the protein composition. The sensitising solutions mimicthe effects of demineralisation in order to detect hypersensitivity anderosion and may be used to assess the extent of a particular problem.For example, an acid solution may be used to identify areas of dentine(e.g. from tooth erosion) or root exposure (e.g. from receding gums).This is because particular parts of the tooth will respond more stronglyto acid solutions than other parts and so can be identified. Forexample, due to the lower extent of mineralization within dentine andcementum, compared to enamel, addition of a sensitising solution willcause the release of more calcium from the dentine and cementum than theenamel. Upon application of the ion-sensitive reporter, the regions ofdentine (corresponding to regions of dentine erosion orhypersensitivity) will be brighter, i.e. with a stronger optical signal,than regions of enamel so indicating the extent of the problem. This mayimprove the accuracy of the results.

Sensitising solutions may also be used to assess the susceptibility ofan individual for a particular condition. Those individuals moresusceptible to tooth erosion will show more demineralisation and so agreater response. Enamel structure and make up is less important inassessing susceptibility to dental erosion than saliva. Salivarycomposition, volume, composition and flow pay an important role indetermining an individual's erosion susceptibility. The technology ofthe invention may be able to determine the resistance of the toothenamel to acid challenge including the protection afforded by theindividual's saliva (in particular the salivary pellicle). Such aquantitative test may be beneficial to dentists and dental hygienists todetermine patient susceptibility and to monitor treatment and toothpastedevelopers and food scientists wanting to understand what effect changesto formulations have on level of demineralisation. Additionally thistest will be useful in the promotion of new erosion prevention coatings.Therefore, an alternative version of the test for demineralisation dueto erosion may involve waiting for a period of time, for example lessthan 1, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18,19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29 or 30 seconds after exposureto the eroding solution so that the saliva can build up in the mouth,and then testing the extent of demineralisation with the detectioncomposition. The period of time could be extended as necessary up to 1,2 or 5 minutes for the saliva to build up again.

The resulting optical signal may be detected using a spectrophotometer,charge coupled device (CCD), complementary metal-oxide semiconductor(CMOS), digital camera, intensified camera, photographic film,fibre-optic device, photometric detector, photomultipliermicro-electro-mechanical system (MEMS) or visually by eye. Forlaboratory testing, for example in the development of tooth-friendlydrinks, the process may use a camera, luminometer or fluorometer forautomation and high throughput of samples.

Software may be used to analyse the intensity of the light, the locationof the light and the duration of the light produced. It can be used toenhance the signal and provide a “superimposed” overlay on an image ofthe teeth to enable dentists to accurately target the sites and to aidin monitoring changes in time or after treatment.

Thus, the present invention also allows the assessment of the potentialfor further erosion, as well as dentine hypersensitivity (throughdemineralisation causing further opening of exposed dentinal tubules),by determining the amount of free calcium. Thus, the method allows theidentification of patients more susceptible to tooth erosion, as well ashypersensitive teeth. This would allow preventive measures to be adoptedby those individuals who are prone to erosion and may also allowlaboratory-based tests to investigate new toothpastes forhypersensitivity, or to analyse food or drink products for theirtooth-eroding properties.

The following experiments were carried out using an image basedluminescence technique and the ion-sensitive protein aequorin. All workwas carried out using extracted human teeth. In the mouth, a variety ofmethods of application could be used. For example, there may be acarrier device for the disclosing composition. This may be a mouthpiecesuch as a dental tray. An advantage of using a carrier device is that itkeeps saliva away from the tooth and the disclosing composition. Thetray may be non-customised i.e. only has approximate shape and size ofperson's mouth, or customised i.e. uses a person's teeth as a templateto make the tray. The tray would act as an interface between thedisclosing composition and the detector. Preferably the carrier deviceis optically clear. The disclosing composition may be added to carierdevice before being placed in a patient's mouth or injected in tocarrier device when in the mouth. Alternatively a strip of thedisclosing composition may be used. This would be akin to toothbleaching strips known in the prior art, which are applied to the areaof interest. Conventional bleaching strips comprise a flexible plasticstrip coated with a dental bleaching gel of moderate viscosity andrelatively low stickiness on the side of the strip facing the user'steeth. Alternatively the disclosing composition could be sprayed onteeth or applied in a mouthwash.

An aequorin solution was prepared as follows. Recombinant aequorin wasexpressed in E. coli using the gene sequence originally from AequoreaVictoria, complexed with the substrate coelenterazine, and lyophilized.The dry stock preparation contained approximately 1% aequorin w/w inmannitol (Prolume®). To make a working aequorin solution for applicationto teeth, the dry stock aequorin preparation was dissolved at aconcentration of 1 mg/ml w/v in calcium-free purified water.Alternatively 1 mg/ml w/v aequorin was prepared in 1% Akucell 3625 gelwith 1 mM EDTA. When calcium ions are added to this aequorin solution orgel, a flash of blue light is emitted.

Samples were placed in a dark box on a height-adjustable stage andimages were recorded using a low light charge coupled device or CCD(Starlight Xpress HX-9® thermoelectrically cooled CCD camera fitted witha Tamron® macro lens). In most cases, hardware pixel binning of 2×2 wasused to increase the sensitivity of detection and reduce exposure times.Inages were saved as TIF files. Daylight images were captured with thedark-box door open allowing ambient light to illuminate the samples, andcaptured using 10/100^(th) second exposure and 2×2 binning. Dark imageswere taken with the dark box door closed, and using a 1 or 2 minuteexposure time, with 2×2 pixel binning.

Grayscale (256 levels) images were opened in Image J and (if necessary)the contrast adjusted to increase the clarity of the image, before beinginserted to Microsoft Word® document. For images produced for the sameexperiments the same adjustments were made to each image. The resultingimages can be used to map the luminescence, corresponding to thepresence of calcium on the sample. The darkest regions (black) indicateregions of lowest light and the lighter regions (white) indicate regionsof increasing light.

Experiment A: Demineralisation of Teeth Using Acid Gel

A standard method used in the industry to mimic generation of activecaries in the laboratory is to create regions of demineralisation usingacid solutions or gels (for example reference Amaechi et al.: Arch OralBiol 1998; 43: 619-628). We have carried out similar experiments inorder to determine whether our disclosing material can be used toidentify regions of demineralisation.

Carboxymethylcellulose (3% w/v Akucell 1985) gel was prepared at pH 4.7or pH 6.4 (using 0.1M lactic acid, neutralised with 5M potassiumhydroxide). This pH range was chosen since enamel dissolves at acritical pH of approximately 5.4. ‘Windows’ of approximately 4×4 mm werecreated on the smooth surfaces of extracted premolar teeth using nailvarnish, FIG. 2. Windows were of similar size (since the size is knownto affect the extent of mineral loss). Gel (either pH 4.7 or 6.4) wasapplied to the window and the tooth incubated in a hydrated environmentand 37° C. for 5, 10, 14 or 21 days. replicate teeth were used at eachtimepoint and pH. In addition, 15 teeth were incubated for 14 days ineither gel of pH 4.7, assessed, then incubated with gel of either pH 4.7or pH 6.4 for a further 5 days before being reassessed. This allowsdetermination of whether demineralization can be halted by neutralizingthe gel.

After incubation, the gel was gently wiped from the tooth surface withtissue and the surface rinsed with deionised water. The tooth was imagedwith a Sony HX9 camera using 2×2 binning and image capture time of 10 msin the light. 0.2 cm³ of 1 mg/cm³ aequorin in 1% Akucell 3625 gel(disclosing gel) prepared with 1 mM EDTA was transferred to tooth withan automatic pipettor. A 1 minute image with 2×2 binning was takenimmediately in the dark.

Example images are shown in FIG. 3. The contrast of images was alteredto improve presentation and exactly the same adjustments were applied toall images. Image J was used to determine the brightness of the areawithin the windows, FIGS. 4 and 5.

The results clearly shows that those teeth incubated with gel of pH 4.7showed higher levels of light i.e. free calcium release anddemineralization than those incubated with gel of pH 6.4. Further, lightoutput was reduced when teeth were incubated first in acid gel and thentransferred to neutral gel, as compared to teeth transferred from acidgel to acid gel.

These results provide robust evidence that calcium sensitivephotoproteins such as acquorin can detect areas of demineralization.Significantly, the demineralization could be detected after only 5 days.This is earlier than other techniques described in published literature,providing evidence that this method will provide data for very earlydemineralization.

Experiment B: Use of Alternative Disclosing Materials

There are a number of materials that can be used to identify regions ofdemineralization by determining ion release. Example A used thephotoprotein aequorin. Other materials may also be used.

FIG. 6 shows how obelin (a calcium sensitive photoprotein) may also beused. An extracted tooth was incubated in 1% citric acid for 2 minutes.Acid is known to cause demineralisation of enamel. The tooth wasremoved, rinsed in deionised water then assayed. The tooth was imagedwith a Sony HX9 camera using 2×2 binning and image capture time of 10 msin the light. 0.2 cm³ of either 1 mg/cm³ aequorin or 50 ug/ml obelin in1% Akucell 3625 gel (disclosing gel) prepared with 1 mM EDTA wastransferred to tooth with automatic pipettor. A 1 minute image with 2×2binning was taken immediately in the dark. To improve presentation,image contrast was adjusted using ImageJ; the same adjustment was madeto both images. FIGS. 6A shows light generated from aequorin gel and 6Bfrom obelin gel. Results indicate how a number of different reportersmay be used to indicate the presence of free ions and demineralisation.

Experiment C. Exposure of Roots

An extracted tooth was immersed in aequorin to test whether all areas ofthe tooth responded in the same manner to aequorin solution. The toothwas lightly brushed with calcium-free purified water and placed in a 3cm diameter Petri dish in a dark box. A daylight image was acquiredusing the CCD camera.

5 ml of 1 mg/ml aequorin solution was pipetted directly onto the surfaceof the tooth. An image was immediately acquired, using a 2 minuteexposure, with 2×2 binning. The root of the same tooth was then ‘masked’with liquid latex (CopyDex®) and aequorin solution added again and theimage taken as before. Results are shown in FIGS. 7 a and 7 b.

FIGS. 7 a and 7 b are images of a tooth after exposure to aequorin, anda root of tooth masked with Copydex® before exposure to aequorin,respectively. In FIG. 7A, the lighter areas (greatest luminescence)correspond to the root and in FIG. 7B, there is an absence of light fromthe root area that has been masked. The light output is slightlydifferent due to re-orientation of the tooth following masking. Arrowindicates the presence of caries in the crown of the tooth as evident asa white spot and confirmed by a dental clinician.

Results indicate that the root of the tooth reacts more strongly to theaequorin than does the crown, indicating a much higher amount of freecalcium in the root. This is believed to be because of the lowermineralization of the root tissues (dentine and cementum) than enamel ofthe crown. A calcium-sensitive assay, such as the method describedherein, using aequorin, may be used to identify exposed root tissue,e.g. as part of an investigation of hypersensitivity mechanisms.Alternatively, roots may be masked, e.g. with Copydex®, before additionof the aequorin allowing investigation of the crown without interferencefrom the root.

Experiment D: Exposure of Dentine

Disclosing gels or solutions that identify demineralization due to ionrelease may also be used to detect and assess the extent andlocalisation of demineralisation that results from erosion (andindirectly hypersensitivity).

When the crowns of teeth become chipped—i.e. lose some of the enamel,the dentine of the tooth can be exposed. Similarly when teeth areeroded, e.g. by acid, dentine may be exposed. In this experiment achipped tooth was used to investigate whether exposed dentine can beidentified using a ion-sensitive reporter assay. An extracted tooth waslightly brushed with calcium-free purified water. A portion of enamelchipped off in the process, exposing the underlying dentine. The root ofthe tooth was ‘masked’ with liquid latex (CopyDex®). The tooth wasplaced in a 3 cm Petri dish in a dark box. A daylight image wasacquired. 4 ml of 1 mg/ml aequorin solution was pipetted directly ontothe surface of the tooth. An image was immediately acquired in completedarkness, using a 2 minute exposure, with 2×2 pixel binning. Results areshown in FIGS. 8 a and 8 b.

FIG. 8 a is a daylight image of a tooth and FIG. 8 b is an image of atooth after exposure to aequorin. Circled area shows region of chip.Arrow indicates region of root not fully covered by CopyDex®.

Results indicate that much light was produced from aequorin in contactwith the freshly chipped area of the tooth. This indicates that exposeddentine reacts with aequorin to produce light. An ion-sensitive reporterassay e.g. one using aequorin, could therefore be used to identifyregions where dentine is exposed, for example after tooth erosion.

Experiment E:. Cavity Identification

An extracted tooth was identified to have a cavity by a trained dentalclinician. The root of the tooth was masked using CopyDex®. The toothwas lightly brushed with calcium-free purified water and placed in a 3cm Petri dish in a dark box. A daylight image was acquired using a CCDcamera.

5 ml of 1 mg/ml Aequorin solution was pipetted directly onto the surfaceof the tooth. An image was immediately acquired in complete darkness,using a 2 minute exposure, with 2×2 pixel binning. Results are shown inFIGS. 9 a to 9 b and 10 a to 10 b.

FIGS. 9 a to 9 b are (a) an image of a deciduous (or ‘milk’) tooth inthe light, and (b) a monochromatic image. Following processing of theimage regions of lower light appear in black, with grey and whiteindicating regions of increasing light. The arrow indicates the cavityidentified by dental clinician.

FIGS. 10 a to 10 b are an image of a permanent tooth in the light, and amonochromatic image respectively. Following processing of the imageregions of lower light appear in black, with grey and white indicatingregions of increasing light. The arrow indicates the cavity identifiedby dental clinician.

The composition according to the present invention responds to free ionsby emitting light and the intensity of the optical signal is a measureof the quantity of free ions present. The duration of the light emittedindicates the nature of the ions released, e.g. a longer glow mayindicate a continual release of ions or that released from deepertissues. Different parts of the tooth respond differently to theion-sensitive protein because of the chemical nature of the free ionspresent, e.g. dentine responds more than enamel because of the amount ofmineralization. This can be used to identify tooth active caries, activeerosion, exposed dentine after gums have receded, etc.

The location of the optical signal will indicate the location of theproblem, e.g. the active caries. The size of the surface area of lightindicates the extent of the problem, e.g. the surface area of the activecaries. The duration of the glow can indicate the degree of the problem,e.g. the extent of the effect of the acid-challenge (i.e. the individualsusceptibility of a tooth/patient to caries or erosion) or the type oftissue affected. Active caries may be distinguished from inactive cariesby the intensity, duration or colour of the optical signal produced. Inactive caries demineralisation is continuous so more calcium is presentand more signal is produced. A totally inactive lesion will produce only‘background’ signal levels. A partially active lesion will show areas ofactivity and inactivity, i.e. areas with and areas without signal.

Thus, areas of demineralisation may be detected using ion-sensitivecomplexes prior to clinically visible caries lesion formation so thattreatment, e.g. fluoride application, can be applied to prevent furtherprogress of the decay process.

Experiment F: Caries Identification I

Laboratory studies can be used to create artificial caries, using acidsolutions. Preferably, teeth extracted from the mouth and with cariesare used to test the approach. These will have naturally-generatedcaries and provide a better mimic of teeth in the mouth.

An extracted tooth was identified to have caries by a trained dentalclinician, after identifying a ‘white’ region under a bright light. Thisindicates an area of demineralisation and is a traditional method ofidentifying caries.

The root of the tooth was masked using CopyDex®. The tooth was lightlybrushed with calcium-free purified water and placed in a 3 cm Petri dishin a dark box. A daylight image was acquired using a CCD camera. 5 ml of1 mg/ml Aequorin solution was pipetted directly onto the surface of thetooth. An image was immediately acquired in complete darkness, using a 2minute exposure, with 2×2 pixel binning.

FIGS. 11 a to 11 b are a daylight image of a tooth in the light, and agreyscale image, respectively. Following processing of the image,regions of lower light appear in black, with grey and white indicatingregions of increasing light. The arrow indicates caries identified bydental clinician using traditional methods.

As the images show the ‘white’ region identified by a trained dentalclinician to be a caries lesion (active when the tooth was extracted) isidentified as a brighter area in the aequorin assay. This indicates theaequorin assay can replace traditional ‘by sight’ methods.

Experiment G: Caries Identification, Assessment of Freshly ExtractedTeeth

Teeth that had been extracted for orthodontic or other reasons wereobtained immediately after extraction. No patient information wasavailable, although some of the teeth were predicted by a dentist tohave active caries due to the age (it was a clinic for minors) andcondition of the teeth. Immediately after extraction, teeth were rinsedwith deionised water to remove some of the adhering blood and biologicalmaterial. The teeth were assayed immediately with disclosing gel.

The effect of brushing the extracted teeth in deionised water wasdetermined by comparing light output from brushed and unbrushed teethwith cavitated lesions; FIG. 12. Limited effect was observed and so theremainder of teeth were brushed, as we consider this approach bestmimics a patient's actions when visiting a dentist.

A dentist assessed the teeth for caries lesions and marked which side ofthe tooth to look at with pencil. This side was placed uppermost in apetridish and the tooth was imaged with a Sony HX9 camera using 2×2binning and image capture time of 10 ms in the light. 0.2 cm³ of 1mg/cm³ aequorin in 1% Akucell 3625 gel (disclosing gel) prepared with 1mM EDTA was transferred to the tooth with automatic pipettor. A 1 minuteimage 2×2 binning was taken immediately in the dark.

Image J was used to alter the contrast of images, although differencesare easily visible without image modification, this was carried out inorder to better present the data. Regions of lower light appear inblack, with grey and white indicating regions of increasing light.Results are shown in FIG. 13-16.

Teeth were then x-rayed in order to determine whether the regions ofactive demineralization identified in the photoprotein assay werevisible by traditional methods. Although X-rays are used to monitorlesion progression caries that were detected with the disclosing gelwere not visible by x-ray, FIG. 17. This indicates the usefulness inthis approach for early identification of caries lesions.

Experiment H: Assessment of Interferences

Potential interferences by other products, for example toothpaste wereinvestigated, because if light is produced in response to these thenthis assay could be problematic for in-mouth use.

Saliva: extracted teeth were rinsed in either deionised water or saliva(pooled from 8 individuals). Before addition of disclosing solution theteeth were imaged with a Sony HX9 camera using 2×2 binning and imagecapture time of 10 ms in the light. 5 cm³ 1 mg/ml aequorin in deionisedwater was then added (disclosing solution) and imaged for 2 minutes, 2×2binning in the dark. Teeth were either imaged in saliva, removed fromsaliva or removed and rinsed in deionised water FIG. 18. Resultsindicate that saliva contains significant quantities of calcium.However, providing the tooth is not in volumes of saliva it should notinterfere with analysis. Even in the mouth the volume of saliva will beminimal and so saliva is not expected to be a problem for analysis.

Experiment H2—Calculus

Calculus was obtained by scraping from teeth in the course of a dentaltreatment and was provided as flakes suspended in water. Bothsubgingival and supragingival were assessed. Samples were filteredbefore use with a Millipore membrane filter and holder, under vacuum andwashed with deionised water. 5 cm³ 1 mg/ml aequorin in deionised waterwas added and the samples imaged for 1 minute, 2×2 binning. FIGS. 19 aand 19 b. Contrast was adjusted using ImageJ to improve presentation,the same adjustment was applied to both samples.

The effect of in-situ calculus was also investigated. 5 cm³ 1 mg/cm³aequorin 0in deionised water was added and the samples imaged for 2minute, 2×2 binning, FIG. 20

Experiment H3—.Resin Filling

A tooth with a resin filling was assessed. The tooth was imaged with aSony HX9 camera using 2×2 binning and image capture time of 10 ms in thelight. 0.2 cm³ of 1 mg/cm³ aequorin in 1% Akucell 3625 gel (disclosinggel) prepared with 1 mM EDTA was transferred to tooth with an automaticpipettor. A 1 minute image 2×2 binning was taken immediately in thedark, FIG. 21.

Results indicate that small amounts of light were obtained but arelikely to be too low to interfere with the assay. Indeed lower regionsof light on a tooth may provide an indication of the presence ofcalculus.

Experiment H4—Toothpaste.

Teeth were brushed with deionised water, or toothpaste and deionisedwater before being assessed with 2 cm³ of 1 mg/cm³ aequorin in deionisedwater. No extra light was visible from toothpaste-treated surfaces thancontrols indicating toothpaste should not interfere with the assay (datanot shown).

Experiment I: Dental Erosion and Hypersensitivity

Carbonated soft drinks contain high levels of acid and are known to be acause of tooth erosion and can exacerbate dentine hypersensitivity. Anumber of extracted teeth were incubated in these drinks and aequorinwas used to assess their effects. This was undertaken with a view todeveloping an assay for dental erosion (and indirectly,hypersensitivity) or a method of identifying susceptible individuals.

Extracted teeth were lightly brushed with calcium-free purified waterand toothbrush and placed in a 3 cm Petri dish in a dark box. A daylightimage was acquired using a CCD camera. 5 ml of 1 mg/ml Aequorin solutionwas pipetted directly onto the surface of the tooth. An image wasimmediately acquired in complete darkness, using a 2 minute exposure,with 2×2 pixel binning.

The teeth were then rinsed with calcium-free purified water before beingimmersed in Cola, Irn Bru® or 1% citric acid for 10 minutes. Teeth werethen rinsed with calcium-free purified water before 5 ml of aequorinsolution was added, and the teeth imaged as before. The pH of thesolutions was also assessed (with a Hydrus 300 pH meter®). All wereacidic: Cola: pH 2.38; Irn Bru® pH 2.82; citric acid pH 2.17. Resultsare shown in FIGS. 22 a to 22 c, 23 a to 23 c and 24 a to 24 c.

FIGS. 22 a to 22 c illustrate the effect of a 10 minute immersion inCola. FIG. 22 a is a daylight image of a tooth with no added aequorin;FIG. 22 b is an image of a tooth in darkness after addition of aequorin,without any other treatment; and FIG. 22 c is an image of a tooth indarkness after addition of aequorin and following a 10 minute incubationin Cola.

FIGS. 23 a to 23 c illustrate the effect of a 10 minute immersion in IrnBru®. FIG. 23 a is a daylight image of a tooth with no added aequorin;FIG. 23 b is an image of a tooth in darkness after addition of aequorin,without any other treatment; and FIG. 23 c is an image of a tooth indarkness after addition of aequorin and following a 10 minute incubationin Irn Bru®.

FIGS. 24 a to 24 c illustrate the effect of a 10 minute immersion in 1%citric acid. FIG. 24 a is a daylight image with no added aequorin; FIG.24 b is an image of a tooth in darkness after addition of aequorin,without any other treatment; and FIG. 24 c is an image of a tooth indarkness after addition of aequorin and following a 10 minute incubationin 1% citric acid.

Drinking carbonated drinks is known to cause tooth erosion. Results hereshow that after incubation with sugary carbonated drinks or acidsolution, free calcium is released from teeth, which can be detectedwith aequorin. This was most pronounced on the root. Ion-sensitiveproteins, such as aequorin, can therefore be used to indicate areas ofcalcium release and so indicate areas of demineralisation and in turntooth damage such as erosion or increased likelihood ofhypersensitivity.

In hypersensitive teeth, the dentine has more tubules open at thedentine surface (up to 8 times) and the tubule diameter is wider. Thisprovides a greater available surface area for demineralisation, forexample by acidic drinks, and will also lead to the release of morecalcium following application of such products. This will be observed asa brighter region, as seen in FIGS. 22 to 24.

Experiment J: Acid Etched Teeth

Dental etching gel is used to roughen the tooth surface so that, forexample, fissure sealants can be attached firmly. The etching gel is anacidic preparation that etches to a limited depth in a localised area.

Extracted teeth were lightly brushed with calcium-free purified waterand toothbrush. A small (4×4 mm) label was applied to the tooth, andfixed in place by painting over the entire area of the label andsurrounding surface of the tooth with nail varnish. This was allowed todry then the label was peeled off, giving a 4×4 mm exposed areasurrounded with varnish. This delimited the area to which the dentaletching gel (Ultradent Products Inc) was applied. Etching gel was leftfor 5 minutes before being wiped off with a cotton swab, and rinsed offwith damp cotton wool swabs.

5 ml of 1 mg/ml Aequorin solution was pipetted directly onto the surfaceof the tooth. An image was immediately acquired in complete darkness,using a 2 minute exposure, with 2×2 pixel binning. A second image wasacquired immediately afterwards, using a 2 minute exposure. Results areshown in FIGS. 25 a to 25 c.

FIGS. 25 a to 25 c are a daylight image, with no added aequorin; amonochromatic image after addition of aequorin, with 2 minute exposure;and a monochromatic image after addition of aequorin, with sequential 2minute exposure. The left arrow indicates nail varnish, the asteriskindicates the area the etching gel was applied to.

When aequorin was added to a tooth that had been etched with dentaletching gel there was a bright flash of light, visible by eye. Thesecond exposure resulted in less light emission than the first exposure.This indicates that the gel releases calcium from only a localised area,this is immediately available for reaction to aequorin, hence the flash,with little ‘subsurface’ calcium being released for light output to beprolonged.

This is unlike the effect observed with citric acid, where light outputcontinued for some time. As shown in FIGS. 26 a to 26 d, the method asdescribed in Experiment E was carried out with a second image, 5 minexposure, and acquired 15 minutes after the aequorin had been added. Itappears that citric acid causes more extensive demineralisation.

FIGS. 26 a to 26 d illustrate the effect of a 10 minute immersion in 1%citric acid. FIG. 26 a is a daylight image, with no added aequorin; FIG.26 b is an image of a tooth in darkness after addition of aequorin,without any additional treatment; FIG. 26 c is an image of a tooth indarkness after addition of aequorin and following a 10 minute incubationin 1% citric acid, 2 minute exposure taken immediately after addition ofaequorin; FIG. 26 d is an image of a tooth in darkness after addition ofaequorin and following a 10 minute incubation in 1% citric acid, 5minute exposure taken 15 minutes after addition of aequorin.

Experiment K: Assessment of a Patient's Susceptibility to Erosion

Different people have a different susceptibility to erosion andhypersensitivity. This is known to be in part due to treatments such asfluorosis and positioning of the teeth although it is generally regardedthat the most important factor influencing dental erosion prevention issaliva (flow rate, composition, buffering and remineralisationcapacity).

The disclosing composition may be used to identify level ofdemineralisation caused by acid erosion of patients by first rinsingteeth in an acid solution. This will provide information on thesusceptibility of the tooth itself for erosion. Further, by reassessinglight output after addition of saliva to the teeth the role of anindividual patient's saliva can be determined. The assays may beperformed on extracted teeth or in the mouth.

To assess of demineralisation, the tooth was imaged with a Sony HX9camera using 2×2 binning and image capture time of 10 ms in the light.0.2 cm³ of 1 mg/cm³ aequorin in 1% Akucell 3625 gel (disclosing gel)prepared with 1 mM EDTA was transferred to tooth with automaticpipettor. A 1 min image with 2×2 binning was taken immediately in thedark. ImageJ was used to determine the brightness of the crown and rootareas. A Glowell™ (blue G2, 96 well format) was included to ensure theuniformity of the light measuring equipment. Importantly, the aequorinis not pH sensitive and light output is similar across a large pH range.Extracted teeth were assessed as above (in triplicate). Teeth wereincubated in 1% citric acid for 2 minutes, removed, rinsed in deionisedwater, assessed, then incubated in either deionised water or saliva for30 s and then reassessed.

FIGS. 27 a and 27 b shows how the saliva has a greater protective effecton the acid-treated enamel than deionised water, resulting in a greaterreduction in light output. Less difference was observed on the rootsurface. Together with Experiment L, which provides evidence for thequantitative nature of the assay this suggests that a similar assaywhereby a patient's teeth are rinsed with acid solution, light outputassessed with a demineralization disclosing solution and the protectiveaffect of saliva determined by reassessing after contact with salivawill provide a method to determine a patient's susceptibility toerosion. This will help in clinical diagnosis, deciding on appropriatetreatment and providing evidence for how lifestyle affects a patient'steeth.

Experiment L: Assessment of the Erosivity of Foodstuffs

Different foodstuffs are known to cause different levels of erosion(e.g. Hemingway et al., British Dental Journal (2006); 201, 439). Thisis partly due to the pH of the foodstuff, and partly due to calciumconcentration. For example, carbonated soft drinks contain high levelsof acid and are known to be a cause of tooth erosion and can exacerbatedentine hypersensitivity.

The disclosing solution and assay method may be used to develop an assayfor dental erosion (and indirectly, hypersensitivity). This may be usedto identify the extent of demineralisation caused by foodstuffs, soproving a risk factor of foods. It may be used to determine theeffectiveness of consumer and clinical products such as toothpastes,mouthwashes, sealants, bleaching agents. It may also be used in thedevelopment and identification of foodstuffs that cause lessdemineralisation and are therefore kinder to teeth.

In hypersensitive teeth, the dentine has more tubules open at thedentine surface (up to 8 times) and the tubule diameter is wider. Thisprovides a greater available surface area for demineralisation, forexample by acidic drinks, and will also lead to the release of morecalcium following application of such products. This will be observed asa brighter region.

Lines were drawn across extracted deciduous teeth with nail varnish todelimit crown and root surfaces. Extracted teeth were incubated insolutions of various pH. These were either various dilutions of citricacid, sodium bicarbonate, phosphate buffered saline or deionised water.The pH of the solutions was also assessed (with a Hydrus 300 pH meter®).Incubations were for 2 minute, after incubation the teeth were removedrinsed in deionised water then assayed. The tooth was imaged with a SonyHX9 camera using 2×2 binning and image capture time of 10 ms in thelight. 0.2 cm³ of 1 mg/cm³ aequorin in 1% Akucell 3625 gel (disclosinggel) was prepared with 1 mM EDTA and transferred to tooth with automaticpipettor. A 1 min image with 2×2 binning was taken immediately in thedark. ImageJ was used to determine the brightness of the crown and rootareas. Glowell™ (blue G2, 96 well format) were included to ensure theuniformity of the light measuring equipment. Experiments were performedin triplicate; averages are shown.

FIG. 28 illustrates how solutions of differing pH lead to differentlevels of demineralisation, as measured by brightness, with solutions oflower pH generating more demineralisation (more brightness). As shown,the root was more susceptible than crown, with more demineralisation atpH 4, which matches well with the available literature, which indicatesthat enamel demineralises at a critical pH of 5.5, whereas the roottissue, which is not protected by enamel demineralises at a critical pHof 6.2. This experiment indicates that the assay is quantitative and canbe used to assess demineralisation resulting from erosion. Disclosinggels or solutions, which identify demineralisation due to ion release,can be used to indicate tooth damage such as erosion or increasedlikelihood of hypersensitivity.

FIG. 29 illustrates how the effect of foodstuffs on demineralization ofteeth can be determined using this disclosing composition and assaymethod. Assay method was as described. Results indicate that the pH ofthe foodstuff has a large affect on the teeth. Again the root surfaceappears more susceptible to pH. The results were not only dependent onthe pH of the foods and other factors appear to be involved. So, thediet drinks coca cola® and Ribena Really Light® produced less light thanmay be expected from their pH.

Disclosing gels or solutions, which identify demineralization due to ionrelease when used in an assay such as this, can be used to determine therisk factors of different food stuffs on teeth or as a tool in thedevelopment of new food stuffs and consumer and clinical products suchas toothpastes, mouthwashes, sealants, bleaching agents. Addition ofother steps, such as incorporation of a saliva wash as shown inExperiment G may also be useful to mimic in mouth conditions.

1. A pharmaceutical composition, comprising a complex capable ofproducing an optical signal characteristic of the presence of free ions.2. A composition for use in detecting active dental caries and/or activetooth demineralisation due to erosion, comprising a complex capable ofproducing an optical signal characteristic of the presence of free ions.3. A composition according to claim 1, wherein the complex is a dye,synthetic ion chelator such as an EDTA-reporter complex or a macrocyclesuch as a crown ether reporter complex, a protein or protein-reportercomplex, a molecular imprinted polymer-reporter complex or molecularprobe.
 4. A composition according to claim 1, wherein at least one ionto be detected is selected from the group consisting of calcium ions,magnesium ions, phosphate ions, carbonate ions, potassium ions,strontium ions, fluoride ions copper ions, chloride ions, zinc ions,lead ions, tin ions, iron ions or organic material such as enamelins. 5.A composition according to claim 1, further comprising apharmaceutically acceptable additive.
 6. A composition according toclaim 5, wherein the additive is a therapeutically active agent.
 7. Acomposition according to claim 6, wherein the active agent is abactericidal or bacteriostatic agent.
 8. A composition according toclaim 1, further comprising a pharmaceutically acceptable excipient. 9.A composition according to claim 6, wherein the excipient is aflavouring or a colouring additive.
 10. A composition according to anyclaim 1, wherein the composition is in a pharmaceutically acceptabledosage form.
 11. A composition according to claim 10, wherein thecomposition is a liquid, a powder, a mouldable substance or a gel.
 12. Acomposition according to claim 1, wherein the composition comprises fromabout 1 ng/ml to about 10 mg/ml complex or a concentration that gives asufficiently high signal to noise ratio.
 13. A composition according toclaim 1, wherein the complex is a protein or protein complex.
 14. Acomposition according to claim 13, wherein the protein or proteincomplex undergoes a conformation change on binding free ions that leadsto an optical signal being generated.
 15. A composition according toclaim 13, wherein the protein or protein complex comprises aequorin,obelin, clytin, mitrocomin, halistaurin, phialidin, mnemiopsin,symplectin, gr-bolinopsin, casein, calsequestrin, calexcitin, calciumbinding cysteine protease, calmodulin and other EF hand proteinsberovin, or mixtures thereof.
 16. A composition according to claim 13,wherein the protein or protein complex comprises tandem fusions of afluorescent protein, calmodulin and a calmodulin-binding peptide (Ml 3).17. A composition according to claim 1, wherein the complex fluorescesat a characteristic wavelength indicative of the presence of ions.
 18. Acomposition according to claim 1, wherein the composition comprises afirst complex which produces an optical signal on binding with freeions, and a second complex which fluoresces at a characteristicwavelength indicative of the presence of free ions.
 19. A compositionaccording to claim 13, wherein the protein or protein complex ismodified to enhance the signal or alter its emission spectra.
 20. Acomposition according to claim 19, wherein the modification of theprotein or protein complex is accomplished through alteration of the DNAsequence of the gene, by acetylation, ethoxycarbonylation,fluorescamine-modification or fluorescein labelling or by creation ofchimeric proteins.
 21. A composition according to claim 13, wherein theprotein or protein complex comprises a recombinant protein.
 22. Acomposition according to claim 1, wherein the composition is opticallytransparent.
 23. A composition according to claim 1, wherein the opticalsignal is detected by a spectrophotometer, charge coupled device (CCD),complementary metal-oxide semiconductor CMOS, digital camera,intensified camera, intraoral camera, videoscope, photographic film,fibre-optic device, photometric detector, photomultiplier,micro-electro-mechanical system (MEMS) or visually by eye.
 24. The useof a composition according to claim 1 for the manufacture of apreparation for use in the detection of dental caries.
 25. The use of acomposition according to claim 24 in the manufacture of a preparationfor use in the differentiation between active and inactive dentalcaries.
 25. The use of a composition according to claim 1 for themanufacture of a preparation for use in the detection of toothdemineralisation due to erosion.
 26. The use of a composition accordingto claim 1 for the manufacture of a preparation for the detection ofsites of dentine demineralisation related to dentine hypersensitivity.27. A method for the detection of tooth demineralisation, comprising thesteps of exposing a tooth to a composition according to claim 1 anddetecting the resulting signal.
 28. A method according to claim 27,further comprising the steps of marking regions of the tooth or toothmodel in order to allow identification of particular regions.
 29. Amethod according to claim 27, further comprising the step of exposingthe tooth to a sensitising solution prior to exposure with thecomposition.
 30. A method according to claim 29, wherein the sensitisingsolution comprises an acidic solution.
 31. A method according to claim29, wherein the sensitising solution comprises a sugar containingsolution.
 32. A method according to claim 29, wherein a period of timeis allowed to lapse in between applying the sensitising solution andapplying the detection composition of claim
 1. 33. A method according toclaim 33, wherein the period of time is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10,11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28,29, or 30 seconds.
 34. A method according to claim 24, wherein detectionis carried out by means of a spectrophotometer, charge coupled device(CCD), complementary metal-oxide semiconductor CMOS, digital camera,intensified camera, intraoral camera, videoscope, photographic film,fibre-optic device, photometric detector, photomultiplier, avalanchephotodiode, light sensitive array, micro-electro-mechanical system(MEMS) or visually by eye.
 35. A kit for use in detectingdemineralisation, comprising; a) a composition comprising aion-sensitive complex according to claim 1; b) means for applying thecomposition, and c) a detector.
 36. A kit according to claim 35, furthercomprising an acidic or sugary sensitising solution.
 37. A kit accordingto claim 35, further including a marker such as a grid for marking areasof interest on a tooth or tooth model.